text: import sys
  import math
  from collections import defaultdict, deque
  
  sys.setrecursionlimit(10 ** 6)
  stdin = sys.stdin
  
  INF = float('inf')
  
  ni = lambda: int(ns())
  na = lambda: list(map(int, stdin.readline().split()))
  ns = lambda: stdin.readline().strip()
  
  N = ni()
  fib = [1, 1]
  for i in range(2, N + 1):
      fib.append(fib[i - 1] + fib[i - 2])
  print(fib[N])